The state of the art for actuators comprising an array of micro actuators is believed to be represented by the following, all of which are US patent documents, unless otherwise indicated:                2002/0106093: The Abstract, FIGS. 1-42 and paragraphs 0009, 0023, and 0028 show electromagnetic radiation, actuators and transducers and electrostatic devices.        U.S. Pat. No. 6,373,955: The Abstract and column 4, line 34-column 5, line 55 show an array of transducers.        JP 2001016675: The Abstract shows an array of acoustic output transducers.        U.S. Pat. No. 6,963,654: The Abstract, FIGS. 1-3, 7-9 and column 7, line 41-column 8, line 54 show the transducer operation based on an electromagnetic force.        U.S. Pat. No. 6,125,189: The Abstract; FIGS. 1-4 and column 4, line 1-column 5, line 46, show an electro-acoustic transducing unit including electrostatic driving.        WO 8400460: The Abstract shows an electromagnetic-acoustic transducer having an array of magnets.        U.S. Pat. No. 4,337,379: The Abstract; column 3, lines 28-40, and FIGS. 4, 9 show electromagnetic forces.        U.S. Pat. No. 4,515,997: The Abstract and column 4, lines 16-20, show volume level.        U.S. Pat. No. 6,795,561: Column 7, lines 18-20, shows an array of micro actuators.        U.S. Pat. No. 5,517,570: The Abstract shows mapping aural phenomena to discrete, addressable sound pixels.        JP 57185790: The Abstract shows eliminating the need for a D/A converter.        JP 51120710: The Abstract shows a digital speaker system which does not require any D-A converter.        JP 09266599: The Abstract shows directly applying the digital signal to a speaker.        U.S. Pat. No. 6,959,096: The Abstract and column 4, lines 50-63 show a plurality of transducers arranged within an array.        
Methods for manufacturing polymer magnets are described in the following publications:
Lagorce, L. K. and M. G. Allen, “Magnetic and Mechanical Properties of Micro-machined Strontium Ferrite/Polyimide Composites”, IEEE Journal of Micro-electromechanical Systems, 6(4), December 1997; and
Lagorce, L. K., Brand, O. and M. G. Allen, “Magnetic micro actuators based on polymer magnets”, IEEE Journal of Micro-electromechanical Systems, 8(1), March 1999.
U.S. Pat. No. 4,337,379 to Nakaya describes a planar electrodynamics electro-acoustic transducer including, in FIG. 4A, a coil-like structure.
U.S. Pat. No. 6,963,654 to Sotme et al describes a diaphragm, flat-type acoustic transducer and flat-type diaphragm. The Sotme system includes, in FIG. 7, a coil-like structure.
Semiconductor digital loudspeaker arrays are known, such as those described in United States Patent document 20010048123, U.S. Pat. No. 6,403,995 to David Thomas, assigned to Texas Instruments and issued 11 Jun. 2002, U.S. Pat. No. 4,194,095 to Sony, U.S. Pat. No. 4,515,997 to Walter Stinger, and Diamond Brett M., et al, “Digital sound reconstruction using array of CMOS-MEMS micro-speakers”, Transducers '03, The 12th International Conference on Solid State Sensors, Actuators and Microsystems, Boston, Jun. 8-12, 2003; and such as BBE's DS48 Digital Loudspeaker Management System.
As is well known, conventional analog speakers are required to exhibit a flat frequency response. The term “frequency response” as known in the art and as used hereinafter is the measure of any system's transfer function, comparing the output signal of the system, to an input signal having constant amplitude but varying frequencies. The frequency response is typically characterized by the magnitude of the system's transfer function, measured in dB, versus frequency, measure in Hz.
This response, in the context of loudspeakers, is generally governed by the equations, known in the art of a vibrating piston in an infinite baffle:
                    P        =                                            2                        ·            π            ·            ρ            ·            S            ·                          f              2                        ·                          (                              A                2                            )                                R                                    (        1        )                            Where:        P stands for the RMS pressure produced by the vibrating piston [N/m2];        A stands for the peak-to-peak vibration amplitude [m];        S stands for the surface area of the vibrating piston [m2];        ρ stands for the density of the medium (i e. air) in which the piston is vibrating [Kg/m3];        R stands for the distance of the measurement point from the face of the piston [m];        f stands for the vibration frequency [Hz];        
Thus, for instance, increasing the frequency f by a factor of 2 results in corresponding increase in the pressure P by a factor of 4 (provided all other parameters remain unchanged).SPL=20·Log10 P/P0  (2)                Where        P0 stands for a constant reference pressure. Typically selected to be the lowest RMS pressure audible to humans or 20 10−6 N/m2         P stands for the piston RMS pressure (see (1)) SPL stands for Sound Pressure Level. The higher the SPL the louder the sound of the speaker as sensed by the listener.        
As readily arises from equation (1), assuming that all the parameters except the frequency f are maintained invariable, and further assuming that the frequency f is doubled (i.e. increasing by one octave), this will result in multiplying the pressure P by 4 and the latter will result (see equation (2)) in increasing the SPL by 12 dB, giving rise to a frequency response of 12 dB/octave. This is not a desired effect since from the listener's standpoint, the speaker should exhibit a flat response across its entire designated frequency range. Thus, for example, increasing one octave (i.e. doubling the frequency) should not affect the generated SPL which should be maintained substantially constant, unless intentionally adjusted by the listener.
Analog speakers exhibit a flat response notwithstanding the specified 12 dB/Octave frequency response, since an analog speaker has an inherent property according to which increase of the frequency f entails a decrease in the peak-to-peak amplitude A. Thus, reverting to equation (1), when the frequency f is doubled, the amplitude A decreases by substantially a factor of 4, thereby maintaining the generated pressure P substantially invariable and, as readily arises from equation (2), the SPL is also maintained substantially constant, giving rise to the desired flat response.
Obviously, when the listener wishes to increase the sound level he may increase the peak-to-peak amplitude A across the entire frequency range.
The disclosures of all publications and patent documents mentioned in the specification, and of the publications and patent documents cited therein directly or indirectly, are hereby incorporated by reference.